Empty-load braking apparatus

ABSTRACT

Empty-load braking apparatus for a railway car in which the cylinder of the fluid operable cylinder and piston means which actuates the brakes is slidably mounted and movement of the cylinder upon actuation of the brakes is opposed by a spring with a lightly loaded car. With a heavily loaded car, a pawl controlled by load responsive means on the car limits the movement of the cylinder so that a greater braking force is applied.

United States Patent 1191 Ludington et a1.

[ 1 Feb. 26, 1974 EMPTY-LOAD BRAKING APPARATUS [76] Inventors: Robert L. Ludington, 3419 Manitou Tr.; Robert M. Holloway, 921 N. Roeske Tr., both of Michigan City, 1nd. 46360 22 Filed: Aug. 3, 1972 21 Appl. No.: 277,811

Related US. Application Data [63] Continuation-impart of Ser. No. 127,277, March 23, 1971, which is a continuation-in-part of Ser. No.

1,266, Jan. 7, 1970, Pat. No. 3,612,230.

52 U.S.C1. 188/195, 188/153R 51 1111.01 B60t 8/22 58 Field ofSearch.; 188/195, 153 R; 303/2211 [56] References Cited UNITED STATES PATENTS 3,023,855 3/1962 Shafer 188/195 8/1968 Simanek et a1. 188/195 X 12/1972 Michellone et a1. 188/195 X Primary Examiner-Duane A. Reger Attorney, Agent, or FirmBrooks l-laidt & Haffner 57 ABSTRACT Empty-load braking apparatus for a railway car in which the cylinder of the fluid operable cylinder and piston means which actuates the brakes is slidably mounted'and movementof the cylinder upon actuation of the brakes is opposed by a spring with a lightly loaded car. With a heavily loaded car, a pawl controlled by load responsive means on the car limits the movement of the cylinder so that a greater braking force is applied.

15 Claims, 16 Drawing Figures PATENTED M12 19 SHEET 7 [IF 7 EMPTY-LOAD BRAKING APPARATUS This application is a continuation-in-part application of our copending U.S. Pat. application Ser. No. 127,277 filed Mar. 23, 1971, which, in turn, is a continuation-in-part of our copending US. Pat. application Ser. No. 1,266 filed Jan. 7, 1970, and now U.S. Pat. No. 3,612,230.

This invention relates to brake mechanisms and, more particularly, to empty and load brake mechanisms for vehicles.

The brake mechanism according to this invention is particularly adapted, among other possible applications, for use on standard railway cars such as are now widely in use on American, Mexican and Canadian railways. The brake mechanisms according to this invention may be used as new or original equipment on the railway cars, or they may be used as replacements or attachments to brake mechanisms presently in operation.

Heretofore, considerable difficulty has been experienced due to the fact that the usual brake mechanisms constructed in accordance with the prior art concepts resulted in over-braking empty railway cars and underbraking loaded railway cars. Some cars were built so that the empty car weight was increased in order to keep from using certain prior art empty and load brake equipment. It is an object of thepresent invention to overcome the difficulties which were inherent with the usual prior art mechanisms.

Another object of this invention is to provide a new and improved braking mechanism which provides a variable braking force depending upon the load being carried by the car and which can be used with standard railway brake mechanisms.

The performance of railway equipment used in the United States is specified by the rules of the Association of American Railroads. The rules of such Association, effective Jan. 1, 1969, include the following Rule 3(b)(6):

Braking Power: All freight cars built new or rebuilt prior to Jan. 1, 1965, offered in interchange, having metal brake shoes, shall have a nominal braking ratio of not less than 50 nor more than 75 percent of the empty car weight, based on a brake cylinder pressure of 50 lbs. per square inch, except refrigerator cars equipped with cast iron wheels which shall have a nominal braking ratio of not less than 50 nor more than 60 percent of the empty car weight based on 50 lbs. per square inch brake cylinder pressure. In interchange.

All freight cars built new or rebuilt on and after Jan. 1, 1965, offered in interchange, having metal brake shoes, shall have a nominal braking force of 75 percent of the empty car weight or as close thereto as possible, but in-no event to exceed 80 percent of the empty car weight, and not less than 18 percent nor more than 35 percent of the gross rail load,

based on a brake cylinder pressure of 50 lbs. per

square inch. In interchange. Accordingly, it is essential that all new or rebuilt freight car braking systems comply with this requirement. In order to comply, some prior art braking'systems employed one cylinder-piston assembly of one size and a second cylinder-piston assembly of a different size. That is, one cylinder-piston assembly was employed for a loaded car condition and .the other cylinder-piston assembly was used when the car was empty. Under certain conditions both cylinders were used and two reservoirs of air had to be used which was costly in fabrication as well as consuming more air than was required with conventional equipment. This dual system was complicated and expensive to fabricate. Another prior art system employed a single piston and cylinder assembly wherein air pressure was exerted against the front of the piston only when the car was loaded and air pressure was exerted against the front and a portion of a back of the piston when the car was empty. This system worked to some extent, but it required a complicated and expensive piston and cylinder piping arrangement. It will be appreciated that air piping on a railroad car has certain disadvantages not only because of the expense and difficulty of installation thereof but also care must be exercised to eliminate any low spots in the piping where water can accumulate and, in winter, freeze, thereby plugging the air line. Also, large volumes of additional air were required for prior art mechanisms.

In the system described in U.S. Pat. No. 3,335,825, of which we are co-inventors, a compound fluid piston was used which had a first stroke length with one piston diameter and a second stroke length with the second piston diameter. This system is very effective for many installations. The present invention concerns improvements thereover.

In the apparatus described in said copending U.S. Pat. application Ser. No. 127,277, a housing containing a rod and a spring interposed between the housing and the rod is connected in the brake rigging of a railway car so as to control the braking force applied to the car brakes. A pawl on the housing is controlled by car load responsive apparatus so that with light car loads force is transmitted from the housing to the rod, or vice versa, through the spring and so that with heavy loads a rigid connection is provided between the housing and the rod. Such apparatus requires the addition of such housing, rod and spring in some portion of the rigging which, in some cases, requires modification of the rigging which usually is undesirable, particularly where space is limited.

The present invention relates to an improvement in the invention set forth in said copending U.S. Pat. application Ser. No. 127,277, and while it requires modification of the mounting of the conventional fluid operable cylinder and piston means employed to actuate the brakes, the modification is simple and requires little additional space. In addition, it is unnecessary to modify or alter the cylinder and piston means or the brake rigging, and the invention may be used to adapt existing equipment as well as on new equipment.

In the preferred embodiment of the invention, the cylinder of the fluid operable cylinder and piston means employed to actuate the brakes is slidably mounted on the car so that when fluid under pressure is supplied to the cylinder, the cylinder and piston move in opposite directions, the piston rod being connected to the brake rigging and moving in the brake applying direction. A spring acting between the cylinder and the car opposes movement of the cylinder when the car is lightly loaded so that the braking force applied to the brake rigging is limited to that of the spring force applied to the cylinder when the piston completes its stroke. When the car is heavily loaded, means responsive to the load on the car causes a pawl to engage a portion of slidable mounting for the cylinder, which,

in effect, bypasses the spring and which limits the movement of the cylinder to less than the movement permitted by the spring. The braking force applied to the rigging is, in such case, determined by the cylinder and piston means force in the absence of the spring and substantially as though the cylinder were fixed in position, the braking force then being a maximum and greater than when the cylinder is permitted to move against the spring. Of course, if desired, although not preferred, the cylinder and piston may be interchanged, that is, the piston rod may be slidably mounted on the car in place of the cylinder and the cylinder may be connected to the rigging, the spring opposing movement of the piston rod.

Railway cars have a stationary truck side frame and a truck bolster mounted for vertical movement, the vertical position being determined by the load carried by the railway car. In the preferred embodiment of the invention, the load responsive means for controlling the pawl hereinbefore described is a cable connected to either the frame or the bolster, or both, so as to be movable in accordance with the relative positions of the frame and the bolster. Preferably, the cable is connected to the pawl through a conical, helical spring having frictionally engaging turns so as to reduce the possibility of false operation of the pawl due to relative movement of the frame and the bolster which occurs when the car is in transit and which is not indicative of the car load.

Various objects and advantages of the invention will be apparent from the following detailed description of presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic, plan view of a portion of a railway car having the braking apparatus of the invention mounted thereon;

FIG. 2 is a partly enlarged, perspective view, partly in cross-section, oof a portion of the apparatus shown in FIG. 1;

FIG. 3 is an exploded, perspective view of most of the apparatus shown in FIG. 2;

FIGS. 4 and 5 are plan views, partly in cross-section, of the cylinder and piston means and its mounting shown in the preceding figures, and illustrate the operation of such means and the control therefor when the railway car is lightly loaded;

FIGS. 6-8 are views similar to FIGS. 4 and 5, illustrating the operation of the cylinder and piston means and the control therefor when the car is heavily loaded;

FIG. 9 is a graph illustrating the relationship between braking ratio percent and car loading percent;

FIGS. 10-12 are enlarged, side elevation views, partly in cross-section, of the spring damping means illustrated in FIGS. 2 and 3; and

FIGS. 13-16 are schematic diagrams illustrating the use of the invention in connection with various types of brake riggings conventionally used on railway cars.

FIG. 1 illustrates a portion of a conventional type of railway car having a frame 10 and a truck indicated generally by the reference numeral 11. The wheels 12, which support the truck 11, are engageable by a plurality of brake shoes (not shown) which are actuated by brake rigging which comprises rods 13 and 14 and a lever 15 and which usually comprises a brake slack adjuster (not shown). The lever 15, and hence the brake rigging, is actuated by a conventional cylinder and piston means 16, the cylinder 17 of which is mounted on a longitudinal beam 18 of the car and the piston rod 19 of which is pivotally connected to the lever 15.

Normally, the cylinder 17 is secured in a fixed position on the longitudinal beam 18, but in accordance with the invention the cylinder is slidably mounted on the beam 18. Thus, in the preferred form of the invention, the cylinder 17 is mounted on a shear plate 20 which is slidably mounted on a mounting plate 21 secured to the usual mounting 22 (FIG. 3) for the cylinder 17. When fluid, such as air, under pressure is supplied to the cylinder 17 by conventional means and through a hose or pipe 23, the rod 19 moves to the right, as viewed in FIG. 1, to apply the brakes and, unless restrained, the cylinder 17 would move to the left. When the car is empty or lightly loaded, such movement of the cylinder 17 is opposed by a spring 24 extending between the left end of the cylinder 17 and a stop 25 extending from the mounting plate 21. When the car is heavily loaded, movement of the cylinder 17 to the left is limited by a pawl 26 which engages the shear plate 20. The pawl 26 is controlled in position by a cable assembly 27 which is actuated in accordance with the spacing between the truck side frame 28 and the truck bolster 29, such spacing varying with the load on the car.

As shown in FIG. 2, the cable assembly 27 comprises an inner wire or cable 30 and an outer sheath 31. The outer sheath 31 is secured at one end to a bracket 32 mounted on and secured to the bolster 29, and the inner cable 30 passes through a bracket 33 mounted on and secured to the truck side frame 28. A washer 34 is adjustably secured to the end of the cable 30. The opposite end of the sheath 31 is secured to a cup 35 which encloses a spring 36 and telescopically receives a second cup 37 secured to an extension 38. The opposite end of the cable 30 has a sliding fit with a washer 39 secured to the cup 37, passes through a conical, helical spring 40 having frictionally engaging turns and is secured to a washer 41 slidable within the cup 37.

The extension 38 is pivotally connected to an arm 42 secured to a rotatably mounted shaft 43 (FIG. 3) to which the pawl 26 is secured. Accordingly, when the bolster 29 moves downwardly with respect to the frame 28 due to loading of the car, the spacing 44 between the brackets 32 and 33 increases causing the cable 30 to move with respect to the sheath 31 and thereby drawing the cup 37 into the cup 35 and causing the arm 42 and the pawl 26 to rotate clockwise as viewed in FIG. 2. The spacing 44 may increase as much as 2 inches with loading of the car, and when there is a predetermined increase in the spacing 44, the pawl is rotated into the path of the shear plate 20 and arrests the latter.

The piston rod 19 is received within a sleeve 45 secured to a piston 46 which is urged to the left, as viewed in FIG. 2, by a spring 47. The piston 46 is moved to the right by the braking fluid and is limited in such movement by the end wall 48 of the cylinder 17.

As shown in FIG. 3, the mounting plate 21 has a pair of channels 49 and 50 which slidably receive the edge portions of the shear plate 20 and has an opening 51 through which the pawl 26 can extend when the car is heavily loaded. The stop 25 preferably is formed by a bent-up portion of the mounting plate 21 and has an opening 52 therein through which the fluid hose or pipe 23 passes. An extension 53 extends from the stop 25 and has an opening 54 into which the cup 35 fits, the cup 35 being secured to the extension 53.

Movement of the cylinder 17 to the right is limited by a stop plate 55 which is secured to the mounting plate 21 at the righthand ends of the channels 49 and 50. Preferably, the position of the stop plate 55 and the length of the spring 24 are such that movement of the cylinder 17 to the right is limited to less than that which would occur under the urging of the spring 24 and in the absence of the stop plate 55. lnother words, the spring 24 is always at least partially compressed by the cylinder 17.

The fluid hose or pipe 23 is secured to the end portion 56 of the cylinder 17 by a flanged member 57.

The arm 42 and the shaft 43 secured thereto are rotatably mounted by a pair of brackets 58 and 59 which are secured to the back side of the mounting plate 21 on opposite sides of the opening 51, such as by welding. The pawl 26 is mounted on the shaft 43 between the brackets 58 and 59 and is secured thereto by a set screw 60.

FIGS. 4 and 5 illustrate the operation of the apparatus of the invention when the railway car is in a lightly loaded condition. Prior to the application of the brakes, i.e., the supply of fluid under pressure between the piston 46 and the end wall 61 of the cylinder 17, the parts have the positions illustrated in FIG. 4. As shown therein, the piston 46 is moved to a position against the end wall 61 by the spring 47, and the cylinder 17 and the shear plate 20 are urged to the right by the spring 24, movement of the shear plate 21) being limited by the stop plate 55.

When the cylinder and piston means 16 is actuated by supplying fluid under pressure between the piston 46 and the end wall 61 and the car is lightly loaded, the pawl 26 has the position shown in FIGS. 4 and 5 and the cylinder 17 and the piston 46 will assume the position shown in FIG. 5. It will be noted that the piston 46 is limited in movement by the end wall 48 of the cylinder l7 and once it has reached such position the further application of fluid under pressure will no longer cause relative movement between the piston 46 and the cylinder 17. Therefore, when the piston 46 has reached its full stroke, the braking force applied to the lever by the piston rod 19 depends upon the extent to which the spring 24 has been compressed between the cylinder 17 and the stop 25 at the time that the piston 46 engages the end wall 43. In other words, the braking force applied to the lever 15 is limited to the force applied to the cylinder 17 by the spring 24 at the time that the piston 46 engages the end wall 48.

FIGS. 6& illustrate the operation of the apparatus of the invention when the car is heavily loaded and the pawl 26 has been moved to the position shown in FIGS. 6-8 by the load responsive apparatus comprising the cable assembly 27, etc., hereinbefore described. As shown in FIG. 6, the cylinder 17, the piston 46, the shear plate 20, the spring 24 and the piston rod 19 have the relative positions shown in FIG. 4 prior to the introduction of fluid into the cylinder 17. When fluid under pressure is first supplied between the piston 46 and the end wall 61, the cylinder 17 moves to the left as shown in FIG. 7 until the shear plate engages the pawl 26. Of course, at the same time, the piston rod 19 moves to the right as viewed in FIG. 7, applying a light force to the lever 15 which may be only sufficient to tighten the brake rigging.

As the fluid continues to enter the cylinder 17, the piston 46, and hence the rod 19, continues to move to the right, but since the shear plate 20 is held stationary by the pawl 26, the cylinder 17 no longer moves to the left. Accordingly, the braking force applied to the lever 15 is that which is applied to the piston 46 by the fluid in the cylinder 17.

- It will be apparent from the foregoing that when the car is heavily loaded and the pawl 26 is in the position shown in FIGS. 6-8 in which it arrests the shear plate 20 and hence the cylinder 17, thhe braking force is determined by fluid pressure and the size of the piston 46. However, by suitably selecting the spring 24 in relation to the maximum stroke of the piston 46, it is possible to limit the maximum braking force applied to the lever 15 to a lower value with the pawl 26 in the position shown in FIGS. 4 and 5. The spring 24 may, for example, be a spring of the type normally employed between the truck bolster and the truck side frame to support the bolster.

FIG. 9 is a graph illustrating one manner in which the apparatus of the invention may be adjusted for opera tion of the brakes. In FIG. 9, curve 62 illustrates the variation of braking ratio percent with car loading percent when the pawl 26 is out of engagement with the shear plate 205. Curve 63 illustrates the variation of braking ratio percent with car loading percent when the pawl 26 engages the shear plate 20, and assuming a normal brake line air pressure. Curve 64 illustrates the variation in braking ratio percent with car loading percent, assuming the same piston size and an increase in air pressure to a higher value, such as can occur with emergency braking. If the cylinder 17 were held in a fixed position it is apparent from an examination of curves 63 and 64 that although the braking ratio percent would not decrease below 20 percent with a fully loaded car, nevertheless, the braking ratio percent would far exceed the required percent hereinbefore discussed when the car loading is less than about 15 percent. However, if the pawl 26 and its associated load responsive control are set so that the pawl 26 is disengaged from the shear plate 20 when the load on the car is about 44 percent or less, then the braking ratio percent changes from curves 63 and 64 at about 44 percent of the car loading to that obtained from the curve 62, so that even with no load on the car the braking I ratio percent does not exceed 75 percent. Curves similar to 63 and 64 with higher air pressures may also be drawn, but even if higher air pressures, e.g. as much as about twice the normal pressure, are employed, such as the case under certain operating conditions, the braking ratio percent will not exceed 75 percent or be less than 20 percent with the apparatus of the invention.

As an example, which does not necessarily represent the optimum conditions, let is be assumed that the spring 24 exerts a pressure on the cylinder 17 of ap proximately lbs. when the parts have the relative positions shown in FIGS. 4 and 6, and that the piston 46 has a maximum stroke of 10 inches, and a normal stroke of 5 inches with the cylinder 17 held in the position shown in FIG. 6..If the shear plate 20 is not restrained by the pawl 26, the spring 24 will then be reduced in length by 5 inches when the piston 46 has reached its maximum stroke. With the use of a conventional spring having an inside diameter of 4 inches as the spring 24, the force applied to the cylinder 17, and hence the lever 15, by the spring 24 can be about 2,800 lbs. when the spring 24 is so compressed. With conventional brake rigging, a force of 2,800 lbs. applied to the lever will produce a braking force of approximately 27,330 lbs. which means that the empty car weight can be as low as about 36,440 lbs. without the braking force exceeding 75 percent of the empty car weight. On the other hand, if the cylinder 17 is held in a fixed position, the same piston with the same brake rigging and a 50 lb. per square inch air pressure would produce a braking force-of approximately 54,650 lbs. which means that the empty car weight must be about 75,870 lbs. if the braking force is not to exceed 75 percent of the empty car weight. Accordingly, with the apparatus of the invention, the weight of the empty car can be reduced by approximately 18 tons which can be used to increase the payload of the car.

Although operation of the pawl 26 to. engage the shear plate 20 at a car loading percent of about 44 percent provides the results illustrated in FIG. 9, it will be apparent to those skilled in the art that the braking ratio percent may be maintained between the desired 20 and 75 percent limits if the pawl 26 engages the shear plate 20 when the car loading percent is between about 22 and about 44 percent.

FIGS. 10-12 illustrate in detail the operation of the spring interconnection between the cable 30 of the loadresponsive control apparatus and the arm 42 which operates the pawl 26. When the car loading has reached about 44 percent, the pawl 26 engages the edge of the opening 51 as illustrated in FIGS. 6-8 which prevents further movement of the arm 42, and therfore, an interconnection between the cable 30 and the arm 42 which will permit further movement of the cable 30 in the absence of movement of the restrained arm 42 is required. In addition, when the railway car is in motion, the distance between the truck side frame 28 and the truck bolster 29 varies with movement of the car due to the rounding of curves and irregularities in the road bed. It is desirable to minimize oscillation or movement of the pawl 26 with such movement of the car and the double spring arrangement shown in FIGS. 10-12 performs such function as well as permitting movement of the cable 30 when the arm 42 is restrained.

FIG. 10 illustrates the relative positions of the cups 35 and 37 and the springs 36 and 40 to which the parts are adjusted when the railway car is stationary and empty. As shown in FIG. 10, the cable, which is secured to the washer 41, moves the cup 37 outwardly of the cup 35 assisted by the pressure of the spring 36 against the washer 39 secured to the cup 37. The extension 38, which is pivotally connected to the arm 42, moves it and the pawl 26 to the positions shown in FIGS. 4 and 5. The spring 36 is selected relative to the spring 40, which is a conical, helical spring having frictionally engaging turns, so that the spring 36 is more easily compressed than the spring 40.

When the load on the car is sufficient to actuate the pawl into the position in which it engages the shear plate 20, for example with the car loaded to 44 percent of its maximum loading, the cable 30 moves the parts to the positions shown in FIG. 11. Thus, the washer 41 is still in engagement with the end wall of the cup 37, but by virtue of the engagement of the spring 40 with the washer 39, the cup 37 has been moved inwardly of the cup 35 and the spring 36 has been compressed. Such movement of the cup 37 causes the arm 42, and hence the pawl 26, to move into the position shown in FIGS. 68.

Thereafter, if the load on the car is increased or the bolster moves downwardly caused by bouncing or leaning of the car, the spring 40 is compressed as shown in FIG. 12, but movement of the cup 37 inwardly of the cup 35 and compression of the spring 36 is prevented by reason of the fact that the pawl 26 and the arm 42 are restrained because of the engagement of the pawl 26 with a wall of the opening 51. However, if the cable 30 attempts to move rapidly in the opposite direction by reason of the reduction in the spacing 44 (FIG. 2) due to movement of the bolster 29 toward the frame 28, movement of the washer 41 into engagement with the cup 37 is retarded by virtue of the frictional engagement of the turns of the spring 40. On the other hand, if the decrease in the spacing 44 persists, such as by reason of a reduction in the load of the car, the washer 41 will engage the cup 37, and if the load is less than about 44 percent of the maximum load, the cable 30 and the washer 41 will move the cup 37, and hence the pawl 26, into a position in which the pawl 26 is out of the path of movement of the shear plate 20.

FIGS. 13-16 illustrate diagrammatically the use of the apparatus of the invention in conjunction with conventional brake rigging arrangements. Although not illustrated in such figures, the brake rigging may include a conventional slack adjuster such as the slack adjuster shown and described in US Pat. No. 3,001,612, connected in the rigging in the conventional manner.

FIG. 13 illustrates the use of the apparatus of the invention in conjunction with brake rigging conventionally used with box cars having a bottom connection between the brakes which extends through the truck bolster. The piston rod 19 is connected to the live lever 15, which is connected intermediate its ends to the pull rod 13 and which is connected at its opposite end to the pull rod 14. The second pull rod 14 is connected to a first brake shoe mechanism indicated generally by the reference numeral 66 and which comprises brake shoes 67 and 68. The first pull rod 13 is connected by a lever 69 and a pull rod 70 to a second brake shoe mechanism 71 which comprises brake shoes 72 and 73.

FIG. 14 illustrates the conventional brake rigging for a box car having a bottom connection under the truck bolster, and the lever 15 is connected to brake shoe mechanisms 77 and 78 respectively comprising brake shoes 79 and 80 and brake shoes 81 and 82 by the pull rods 13 and 14, a lever 74 and a pull rod 76.

FIG. 15 illustrates the apparatus of the invention in conjunction with the conventional brake rigging for hopper cars having a bottom connection through the truck bolster. As shown in FIG. 15, the piston rod 19 is connected intermediate the ends of a lever 83 which is fulcrumed from the car body at 84 and which is pivotally connected at its opposite end to a pull rod 85. The pull rod 85 is connected through levers 86 and 87 and pull rods 88, 89 and 90 to brake shoe mechanisms 91 and 92, comprising brake shoes 93-96.

FIG. 16 illustrates the use of the apparatus of the invention in conjunction with brake rigging conventional for a hopper car having a bottom connection under the truck bolster. The piston rod 19 is similarly connected to the lever 83 which is connected to the brake shoe mechanisms 97 and 98 comprising brake shoes 99-102,

through pull rods 85, 89, 103 and 104 and levers 86 and 87.

Although the invention has been described in conjunction with preferred embodiments, it will be apparent to those skilled in the art that various modifications thereof may be made without departing from the principles of the invention.

What is claimed is:

1. Apparatus for operating the brakes of a railway car comprising fluid operable means having a pair of members movable relative to each other with the supply of fluid under pressure thereto, means for movably mounting one of said members on said car, spring means opposing movement of said one member in a predetermined direction, means for connecting the other of said members to said brakes, and control means for alternately limiting said movement of said one member to a first predetermined distance less than that permitted by said spring means and permitting movement of said one memeber in said direction by a second predetermined distance greater than said first predetermined distance.

2. Apparatus as set forth in claim 1, wherein said members are a cylinder and a piston therein having a piston rod extending from said cylinder.

3. Apparatus as set forth in claim 2, wherein said cylinder is said one member which is movably mounted.

4. Apparatus for operating the brakes of a railway car comprising fluid operable means having a cylinder and piston movable relative to each other with the supply of fluid under pressure thereto, said piston having a piston rod extending from said cylinder, means for movably and slidably mounting said cylinder on said car, spring means opposing movement of said cylinder, and means for limiting said movement of said one member to less than that permitted by said spring means, comprising means engageable with the slidable portion of said mounting means for locking the latter in a predetermined position.

5. Apparatus as set forth in claim 4, wherein said means engageable with the slidable portion of said mounting means comprises a pawl and further comprising cable means secured to said pawl for moving said pawl into and out of engagement with said slidable portion.

6. Apparatus for operating the brakes of a railway car comprising a mounting plate adapted to be secured to said car, a shear plate slidably mounted on said mount ing plate, a fluid cylinder mounted on said shear plate for movement therewith, a piston within said cylinder and movable with respect to said cylinder by fluid under pressure in said cylinder and between said piston and said cylinder, a piston rod mounted on said piston and extending from one end of said cylinder, stop means extending from mounting plate in spaced relation to the other end of said cylinder, spring means mounted between said other end of said cylinder and said stop means for opposing movement of said cylinder, and control means on said mounting plate selectively engageable with and disengageable from said shear plate for limiting movement of said cylinder in the direction of said spring when said control means is in engagement with said shear plate.

7. Apparatus as set forth in claim 6, wherein said control means comprises a pawl.

8. Apparatus as set forth in claim 6, further comprising a cable connected to said pawl in series with a conical, helical spring having frictionally engaging turns.

9. in braking apparatus for a railway car comprising brakes and brake rigging for actuating said brakes, the combination therewith of load means on said car responsive to the load on said car, fluid operable means on said car comprising piston and cylinder members for actuating said rigging, means connecting one of said members to said rigging, mounting means movably mounting the other of said members on said car, spring means acting between said other member and said car for opposing movement of said other member upon the supply of fluid to said fluid operable means for actuating said rigging, and control means connected to and responsive to said load responsive means and engageable with one of said mounting means and said other member for limiting movement of said other member when the load on said car reaches a predetermined value, whereby a predetermined braking force is applied to said brakes when said load reaches said predetermined value and a lesser braking force is applied to said brakes when said load is less than said predetermined value.

10. Apparatus as set forth in claim 9, wherein said mounting means comprises a mounting plate secured to said car and a shear plate slidably mounted on said mounting plate, said cylinder member is mounted on said shear plate, said piston member has a rod extending from one end of said cylinder which is connected to said rigging, said mounting plate has stop means thereon spaced from the other end of said cylinder and said spring means extends between said stop means and said cylinder.

11. Apparatus as set forth in claim 10, wherein said mounting plate comprises second stop means for limiting movement of said cylinder in the direction in which it is urged by said spring means whereby said cylinder is limited in movement in said last-mentioned direction by said spring means to less than that which would occur in the absence of said second stop means.

12. Apparatus as set forth in claim 10, wherein said control means comprises a pawl engageable with said shear plate. 1

13. Apparatus as set forth in claim 12, wherein said railway car has a frame and a bolster, the relative positions of said frame and said bolster being dependent upon the load on said car, and wherein said load responsive means comprises means responsive to the relative positions of said frame and said bolster.

14. Apparatus as set forth in claim 13, wherein said means responsive to the relative positions of said frame and said bolster comprises a cable connected at one end to one of said frame and said bolster and movable thereby in accordance with the spacing between said frame and said bolster. and means connecting said cable to said pawl for engaging said pawl with said shear plate when said spacing between said frame and said bolster is less than a predetermined amount.

15. Apparatus as set forth in claim 14, wherein said means for connecting said cable to said pawl comprises a conical, helical spring having frictionally engaging turns.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. ,7 4,14 DATED I February 26, 1974 INVENTOR(S) Robert L. Ludington and Robert M. Holloway Itis certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 9 line 36 (Claim 4) replace "one member" by cylinder Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION I "rum No. 3,794,146 Dated February 26, 1974 ROBERT L. LUDINGTON ROBERT M. HOLLOWAY Inventor-(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, line 3 9: "00f" should read -of-- Col. 6, ling-$13: "thhe" should read --the Col. 7, linen; "75,270" should read --72.,s 7o-- 1111 1634 "therfore" should read -ther'efore Col. 9 lihe" "2 0: "vmemeber" should read --me mber-- lihe .5 6: before "mounting" insert -sa id- Signedlhd sealed this 9th day of July 1974.

(SEAL) Attest:

McCOY M. GIBSON ,JR. 0. M RsgALL DANN Attesting Officer I Commissioner of Patents 7 USCOMM-DC 60375-P69 9 U 5 vGOVERNMENT PRINTING OFFICE ISQ 0-166-331 F ORM PO-105O (10-69) 

1. Apparatus for operating the brakes of a railway car comprising fluid operable means having a pair of members movable relative to each other with the supply of fluid under pressure thereto, means for movably mounting one of said members on said car, spring means opposing movement of said one member in a predetermined direction, means for connecting the other of said members to said brakes, and control means for alternately limiting said movement of said one member to a first predetermined distance less than that permitted by said spring means and permitting movement of said one memeber in said direction by a second predetermined distance greater than said first predetermined distance.
 2. Apparatus as set forth in claim 1, wherein said members are a cylinder and a piston therein having a piston rod extending from said cylinder.
 3. Apparatus as set forth in claim 2, wherein said cylinder is said one member which is movably mounted.
 4. Apparatus for operating the brakes of a railway car comprising fluid operable means having a cylinder and piston movable relative to each other with the supply of fluid under pressure thereto, said piston having a piston rod extending from said cylinder, means for movably and slidably mounting said cylinder on said car, spring means opposing movement of said cylinder, and means for limiting said movement of said one member to less than that permitted by said spring means, comprising means engageable with the slidable portion of said mounting means for locking the latter in a predetermined position.
 5. Apparatus as set forth in claim 4, wherein said means engageable with the slidable portion of said mounting means comprises a pawl and further comprising cable means secured to said pawl for moving said pawl into and out of engagement with said slidable portion.
 6. Apparatus for operating the brakes of a railway car comprising a mounting plate adapted to be secured to said car, a shear plate slidably mounted on said mounting plate, a fluid cylinder mounted on said shear plate for movement therewith, a piston within said cylinder and movable with respect to said cylinder by fluid under pressure in said cylinder and between said piston and said cylinder, a piston rod mounted on said piston and extending from one end of said cylinder, stop means extending from mounting plate in spaced relation to the other end of said cylinder, spring means mounted between said other end of said cylinder and said stop means for opposing movement of said cylinder, and control means on said mounting plate selectively engageable with and disengageable fRom said shear plate for limiting movement of said cylinder in the direction of said spring when said control means is in engagement with said shear plate.
 7. Apparatus as set forth in claim 6, wherein said control means comprises a pawl.
 8. Apparatus as set forth in claim 6, further comprising a cable connected to said pawl in series with a conical, helical spring having frictionally engaging turns.
 9. In braking apparatus for a railway car comprising brakes and brake rigging for actuating said brakes, the combination therewith of load means on said car responsive to the load on said car, fluid operable means on said car comprising piston and cylinder members for actuating said rigging, means connecting one of said members to said rigging, mounting means movably mounting the other of said members on said car, spring means acting between said other member and said car for opposing movement of said other member upon the supply of fluid to said fluid operable means for actuating said rigging, and control means connected to and responsive to said load responsive means and engageable with one of said mounting means and said other member for limiting movement of said other member when the load on said car reaches a predetermined value, whereby a predetermined braking force is applied to said brakes when said load reaches said predetermined value and a lesser braking force is applied to said brakes when said load is less than said predetermined value.
 10. Apparatus as set forth in claim 9, wherein said mounting means comprises a mounting plate secured to said car and a shear plate slidably mounted on said mounting plate, said cylinder member is mounted on said shear plate, said piston member has a rod extending from one end of said cylinder which is connected to said rigging, said mounting plate has stop means thereon spaced from the other end of said cylinder and said spring means extends between said stop means and said cylinder.
 11. Apparatus as set forth in claim 10, wherein said mounting plate comprises second stop means for limiting movement of said cylinder in the direction in which it is urged by said spring means whereby said cylinder is limited in movement in said last-mentioned direction by said spring means to less than that which would occur in the absence of said second stop means.
 12. Apparatus as set forth in claim 10, wherein said control means comprises a pawl engageable with said shear plate.
 13. Apparatus as set forth in claim 12, wherein said railway car has a frame and a bolster, the relative positions of said frame and said bolster being dependent upon the load on said car, and wherein said load responsive means comprises means responsive to the relative positions of said frame and said bolster.
 14. Apparatus as set forth in claim 13, wherein said means responsive to the relative positions of said frame and said bolster comprises a cable connected at one end to one of said frame and said bolster and movable thereby in accordance with the spacing between said frame and said bolster and means connecting said cable to said pawl for engaging said pawl with said shear plate when said spacing between said frame and said bolster is less than a predetermined amount.
 15. Apparatus as set forth in claim 14, wherein said means for connecting said cable to said pawl comprises a conical, helical spring having frictionally engaging turns. 